Isomerization in highly excited states of triply charged carbon dioxide ions produced by intense laser fields

It is commonly accepted that the isomerization process primarily occurs in lowly charged molecular states, while highly charged states typically favor a direct fragmentation pathway through Coulomb repulsion. In the current experiment with an intense 800-nm laser field, a three-body isomerization pathway leading to intermediate ${\mathrm{O}}_{2}^{2+}$ formation and subsequent dissociation is observed in highly excited states of ${\mathrm{CO}}_{2}^{3+}$. It is confirmed by the calculated potential energy curves that ${\mathrm{CO}}_{2}^{3+}$ molecular ions in highly excited states with a linear geometry could transition through conical intersections into low-lying states with a bond angle around ${70}^{\ensuremath{\circ}}$ (e.g., ${6}^{2}A1\ensuremath{\rightarrow}{1}^{2}A1$, ${10}^{2}B1\ensuremath{\rightarrow}{1}^{2}B1$), finally leading to oxygen molecule ions formation via isomerization. The present findings demonstrate that isomerization-induced change in molecular structures is a universal and nonnegligible phenomenon, even in triply charged molecular ions, providing insights into the photoinduced ultrafast processes in Earth's primitive atmosphere and benefit the understanding of ${\mathrm{CO}}_{2}$-dominated planetary atmospheres.